The invention disclosed herein pertains to a flapper type valve having a flapper member biased to sealingly engage an annular seat. Flapper valves are particularly useful in flow conduits and well safety valves to permit flow therethrough in one direction and prevent flow in the opposite direction.
A multitude of forms of flapper valves (sometimes called flapper check or back pressure valves) have been known and used for many years to control flow in petroleum industry pipe lines and producing wells. A problem shared by most flapper valves is insufficient bias or rotational closure force to move the flapper into (or "cut") a high mass flow rate stream for closure. The rotational closing force has usually been provided by torsion springs. Many forms of torsion springs have been used in an attempt to develop more flapper closing force, especially when large diameter flapper valves are used on well packers or subsurface safety valves in the vertical position in well conduits where closing springs must initially overcome the weight of flapper valves. The problem is aggravated by the fact that there is usually not space to house a large torsion spring designed to provide maximum closing force in a well packer or subsurface safety valve.
An example of a flapper or back pressure valve utilizing a torsion spring for closure and attachable to a number of forms of well packers, is shown on page 52 of "Otis Products and Services" (OEC 5516), Sep. 1989, a publication of Otis Engineering Corporation, P.O. Box 819052, Dallas, Tex. 75381-9052.
A expendable flapper valve is shown in U.S. Pat. No. 4,813,481 to Sproul et al. This flapper valve assembly includes a frangible valve closure member supported by an elastomeric hinge.
The DUAL FLAPPER VALVE ASSEMBLY of U.S. Pat. No. 4,846,281 to Clary et al, permits a well logging operation to be carried out after gravel packing a well.
A number of torsion spring flapper valves are shown used in the inverted position for well gravel packing operations in U.S. Pat. Nos. 4,378,842, 4,378,847 and 4,420,041 to Patel.
U.S. Pat. No. 4,890,674 to Le covers a torsion spring flapper valve used in a subsurface safety valve which can be closed rapidly without damage to the flapper closure member or safety valve operator tube.
The use of a torsion spring flapper valve as the valve closure member in a surface controlled subsurface safety valve is disclosed in U.S. Pat. No. 4,945,993 to Dickson and Smith.
U S. Pat. No. 4,216,830 discloses a subsurface well safety valve having a hinged flapper closure element connected to an operator element by similar forms of connectors. These connectors are not springs but each has a torsional section.
U.S. Pat. No. 3,356,145 to Fredd for WELL TOOLS depicts the use of a stretched coil spring to bias the flapper valve toward closed position. The publication reference and patents previously referenced are incorporated for all purposes herein.